Smith, who played Lt. Matthew Scott in the late, great "SGU" (see our "shows that ended too soon" gallery), portrays Gordon McClintock, a NASA hero from the pre-Arkfall days who was presumed dead following a space station catastrophe in 2013.

Remember that Ark that crash-landed near Defiance in the most recent episode? It was the Destiny! OK, maybe not, but apparently McClintock was onboard and in a state of suspended animation. When he is revived from the induced sleep, he's overcome with shock and disbelief at the dangerous new Earth of 2046.

As you can see in the sneak peek above, McClintock has flashbacks to both his wife and to what Indogene scientists did to him in the past. No wonder if freaks out Doc Yewll (Trenna Keating) poking at him.

Smith said he had fun shooting the role in Toronto last fall. The show has "very strong writing, the actors are great and the world is very cool," he wrote on Twitter about a month after filming.

"Defiance" tells the story of Earth several years after the arrival of seven alien races sparked 30 years of war, transforming Earth into a radically different world where humans and aliens are attempting to co-exist peacefully. The boom-town of Defiance, which sits atop the ruins of St. Louis, Mo., is the center of the action.

Smith's episode, "I Just Wasn't Made for These Times," airs at 8 p.m. CT June 10 on Syfy.

After wrapping "SGU," Smith starred in the Syfy movie "Red Faction" and recurred on "Gossip Girl" as Max Harding. He's also appeared in episodes of "Warehouse 13," "The Good Wife," "Blue Bloods," "Person of Interest" and in the miniseries "Coma."

The Julliard School graduate has been working in theater, too, with roles on Broadway in "The Columnist" opposite John Lithgow in 2011. This fall he'll return to Broadway, reprising his role as Jim in the American Repertory Theater's production of "The Glass Menagerie" opposite Cherry Jones and Zachary Quinto.